The invention relates to a disc brake, particularly for a commercial vehicle, having a brake caliper in which is accommodated an application device. The brake caliper is held slidably by way of guiding members on a carrier, which is fixed with screws to an axle connection on the vehicle side.
Especially for reasons relating to the operational reliability of a disc brake and ultimately also of the vehicle in which the disc brake is installed, it is necessary to monitor the wear of the brake pads to ensure that necessary replacement of the respective brake pad takes place at the best possible time. In this case, the state of wear of the brake pads, i.e. the abrasion of the respective brake pad, which is connected to a pad carrier plate, should be determined as accurately as possible beforehand.
Particularly from an economic point of view, there is a requirement for optimum timing of the exchange of the brake pads. The aim here is to perform an exchange only when the friction pad has worn down to a permitted minimum thickness. Earlier exchange would conflict with optimizing the application-related operating costs, while exchanging the pad too late would entail impairment of the functional reliability of the disc brake overall.
Various measures are known for detecting the state of wear of the brake pads. For example, the wear of the friction pad can be determined electronically, with a current-carrying cable being passed through the pad carrier plate. The cable is severed when the friction pad wears and emits a detectable signal to a signal transmitter located, for example, in the driver's cab of the motor vehicle.
Apart from this, there are known wear indicators which use a rotary potentiometer to determine a distance moved by an adjusting device during adjustment of the brake pads to compensate for wear travel, and it is likewise possible for this distance to be recognized by the driver of the vehicle, for example, by means of an appropriate indication device.
For visual recognition of the state of wear of the brake pads and/or of the brake disc, DE 36 12 166 C2 discloses the practice of providing the brake support with a marking which, in combination with a correspondingly modified pad carrier plate, is used for wear detection.
Here, the markings on the brake support are produced by appropriate forming, in particular by means of U- or V-shaped recesses in the form of notches.
By their very nature, such recesses, and indeed other necessary formations, have an effect on the strength of the brake support, and notches, in particular, lead to a reduction in fatigue resistance.
Common to all the devices for wear detection is the fact that they can only be seen essentially with the vehicle wheel removed, and this conflicts with optimized use of the device.
It is the underlying object of the invention to develop a disc brake such that it allows simpler visual wear detection with a low outlay in terms of construction.
This and other objects are achieved by a disc brake having a brake caliper in which is accommodated an application device. The brake caliper is held slidably by way of guiding members on a carrier, which is fixed with screws to an axle connection on the vehicle side. The disc brake includes a brake disc, against which brake pads can be pressed from both sides during a braking operation. At least the brake pad on the application side is mounted in a pad well of the carrier in such a way that it can be made to slide in the direction of the brake disc. A device for the visual wear detection of the brake pad and/or brake disc wear is characterized in that, for detecting wear, a pointer element extending in an opposite direction to the brake disc is connected to at least one screw.
An advantage of the invention is that wear detection is now possible without modifying the carrier (brake support) or any other components of the disc brake. In this arrangement, the pointer element, which, according to the invention, extends in the opposite direction to the brake disc, is designed as a separate part and is fixed to the brake support.
This is preferably accomplished at fixing screws, by which the brake carrier is connected to the axle connection on the vehicle side. The term fixing screws is intended to encompass any connector whether a screw, bolt, or the like.
The pointer element can be fixed on one or more of the screws by a frictional and/or positive engagement and, in the first case, the pointer element has a press-fit sleeve, which is pressed onto a screw head of the screws.
The pointer element corresponds visibly to a guide sleeve held in the brake caliper, which moves together with the brake caliper relative to the pointer element, depending on the degree of wear of the brake pad and/or brake disc.
The change which this involves in the distance between a boundary edge of the pointer element and the free end of the guide sleeve can be detected visually from the outside without having to remove the vehicle wheel. This circumstance is a significant improvement over the prior art since it is possible to carry out a wear check at virtually any time and this, of course, leads to an increase in operational reliability.
According to an advantageous aspect of in the invention, provision is made for the pointer element to be provided with at least one marking, preferably a striped marking, which allows particularly simple wear detection and is applied in a permanent manner, thus ensuring that it does not become unrecognizable, even due to the effects of weather.
Instead of being fixed to the single press-fit sleeve mentioned, it is also possible for the pointer element to be fixed to two press-fit sleeves that are mutually adjacent and are each pressed onto a screw head, thereby ensuring that the screws are secured against twisting, preventing the screws from coming loose owing to shocks due to operation.
According to another aspect, the pointer element can be formed by a pointer sleeve, which is pushed onto a screw head and is held captive there, e.g. by means of a lateral fixing screw which is screwed into the pointer sleeve and presses the latter against the screw head.
Still another aspect of the invention is that the pointer element can be produced at a particularly low price and, in principle, can be used universally. In particular, retrofitting to an already installed disc brake is possible without problems, and the pointer element is designed in such a way that it can be connected to either one or the other side of the fixing of the brake support to the axle connection.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.